Tired of being inactive: a systematic literature review of physical activity, physiological exercise capacity and muscle strength in patients with chronic fatigue syndrome.

A systematic review was undertaken to examine whether patients with chronic fatigue syndrome (CFS) differ from healthy sedentary controls in physiological exercise capacity, physical activity level and muscle strength. From the available literature, it can be concluded that patients with CFS perform less physical activity during daily life, and have less peak isometric muscle strength compared to healthy sedentary control subjects. Conflicting data in relation to physiological exercise capacity of patients with CFS have been reported, but the weighted available evidence points towards a reduced physiological exercise capacity in CFS. Future studies should use a wash-out period for medication use, blinded assessments, a priori power calculation and a sedentary control group comparable for age, gender, body weight, body length and current physical activity level.